John Dyson Heydon is a stickler for the letter of the law.
And he has little time for judges who see their role as making law, rather than upholding it.
"Stronger judicial personalities tend to push the weaker into submission," he wrote in an essay subtitled 'The enemy within' on his aged-enforced retirement from the High Court in 2013.
Now he's setting his steely judicial gaze on the trade union movement and the alleged and yet-to-be-uncovered corruption within.
Heydon, on the face of it, is an unsurprising choice as royal commissioner.
A renowned judicial conservative, he was appointed to the High Court in 2003 by the Howard government in a bid to stem what the coalition saw as the court's over-enthusiasm for judicial activism.
Of his reputation as a black-letter judge, he once said: "I wear it as a badge of honour."
In other words, legal precedence and established law are paramount when making judgments.
Heydon eschews judicial activism, the philosophy whereby judges allow their personal views about public policy, among other factors, to guide their decisions.
But if the Abbott government thinks it can rely on Heydon to take a particularly helpful political line with his royal commission, it better think again.
Heydon has a reputation for being his own man.
On the High Court bench he enjoyed a dissent rate of nearly 50 per cent, including his decision to support the Gillard government's right to strike a controversial people-swap deal with Malaysia in 2011.
"With all respect to my colleagues I think it was a field where the government had to be left to run its foreign policies as it saw fit," he says of the case.
And even when he agreed with his colleagues, Heydon preferred to write separate judgments.
But he did collaborate with another judicial figure - Rod Meagher - in 1989 to write a report on the duties and fiduciary obligations of officials of industrial unions of employers and employees.
The report recommended that the finances of trade unions be administered in the same way as companies.
Coincidentally, the Abbott government has legislation before the parliament that aims to subject corrupt union officials to the same penalties that apply to company directors found guilty of fraud.
Since his retirement from the High Court at age 70, Heydon has headed an inquiry into allegations of altered staff contracts at NSW's largest state-owned electricity generator, Macquarie Generation.
Heydon's plan for a relatively quiet retirement - he now rises at 5.15 each day instead of the 3.30 start of his working days - are on hold for at least year while he undertakes his new commission.
